(Addition quiz) Rewrite Listing 5.1 RepeatAdditionQuiz.java to alert the user if an answer is entered again. Hint: use an array list to store answers. Here is a sample run:

/*********************************************************************************
* (Addition quiz) Rewrite Listing 5.1 RepeatAdditionQuiz.java to alert the user  *
* if an answer is entered again. Hint: use an array list to store answers.       *
*********************************************************************************/
import java.util.Scanner;
import java.util.ArrayList;

public class Exercise_11_16 {
	public static void main(String[] args) {
		int number1 = (int)(Math.random() * 10);
		int number2 = (int)(Math.random() * 10);

		// Create a Scanner
		Scanner input = new Scanner(System.in);

		// Create an ArrayList
		ArrayList<Integer> answers = new ArrayList<Integer>();

		System.out.print(
			"What is " + number1 + " + " + number2 + "? ");
		int answer = input.nextInt();

		while (number1 + number2 != answer) {
			if (answers.contains(answer))
				System.out.println("You already entered " + answer);
			else {
				System.out.print("Wrong answer. Try again. What is "
					+ number1 + " + " + number2 + "? ");
				answers.add(answer);
			}
			answer = input.nextInt();
		}

		System.out.println("You got it!");
	}
}